Process of separating a mixture of trimethylamine and ammonia



Aug. 9, 1938. M. R. FENSKE ET AL PROCESS OF SEPARATING A MIXTURE OF TRIMETHYLAMINE AND AMMONIA Filed March 3, 1937 Mrrell. Fenslw Patented Aug. 9, l9 38 UNITED STATES PAT'EN 2,125,905 g '.'rnncns's or snrann'r'ma A mx'runn I Me'mufa. Fenlk'e suite calm,

" Andrews, j Over-brook,

1t: Haas Com any.

' -,'Application: Mai-cii.3,'

This invention relatesfto me-pr ss 6r manulecturing methylamines' and particularly to" a each other and from ammonia.

process for fractionally separatingi -them lfrom In the process of producingthemethylamines from methanol and ammonia catalytically, the product contains all three methylamines, mono-p the unreacted diand tri-, as well as water and, ammonia and methanol. Ondistillation' the trimethylamine forms-a constant boiling mixture with ammonia and also with mono-methylamine.

so that it is impossible to separate these materials completely by distillationr if'lt is possible to remove allthe trimethylam'i'ne Ironi the"n1lxture,

as a. constant boiling mixture,i'provided suillcient' ammonia is present, .then' to-separate themonoand dimethylamines': by ordinary frac- In this way pure monometh-' r ti'onaldis'tillation. V ylamineland pure 'dlrnethylamiue could be pre-. pared butit was impossible to separate the trimethylaminein a pure'state from the ammonia except by chemical means. i

It "is an object ofthis invention to provide a method whereby the constant boiling mixture of trimethylamine and ammonia may be separated completely into its individual components without causing any chemical changes to take place. The present invention is based onthe'fact that the solubilities of trimethylamin'e and ammonia in any given solvent are different, and by suitably arranging the relative amounts of solvent and gas mixture fed into the system in a given time, a complete separation or the tvidcan be attained.

The mixture of trimethylamine and ammonia does not have to correspond in composition to the constant boiling mixture, since any mixture of the two can be saparated in this manner. In the examples chosen to illustrate this invention a mixture approximating that of the constant boiling mixture is used, for the reason that such mixtures are met with more frequently in the process of manufacturing methylamines. The liquid used for the separation of the .two components will determine which of the two remains;

removed as a gas. If an organic solvent, such as triisobutylene, or a petroleum fraction, such as gasoline, kerosene, gas oil or even lubricating oil, is used, the ammonia will pass throughas a gas, leaving the amine dissolved in the liquid.

The process is preferably carried out under 1' oFFIcE P d I a assin h el ia-Pa 937, sen-1 No. 128,140

I superatmospheric pressure and the actual pressure used will be chosen so asv to permit the condensatio'n ofithe, overhead gas to takeplacewitb 1n thejsystem and within the temperature range .of available coolinglwater. Variations in pressureh'ave onlya veryslight eil'ect on the emoiency, of- "the separation. f v g,

' The process'may be carried out many suitable apparatus. such-as is shown in'the drawing attached hereto. The gas mixturetobe separated may be bubbled through the liquid in an appa-: ratus' such as isfshow'n in Figure .1, or it may be run countercurrent to the liquid in'an apparatus V-as'showninFlgure 2;

Referring to the drawingandspeciflcally to Figure 1, a cylindrical vessel-2' having a pipe 3 attached to the bottom, an inlet pipe -4 and outlet pipes' 5 and 5, is mounted ina jacket 1 which completely surrounds the vessel 2'and lower extension The jacket has an inlet pipe 8 and an outlet. pipe 9.' A valve it is inserted in the inletp'fpe 9 to control the flow of heating or cooling liquid to the Jacket. Thermocouples or thermometers II and I2 are/inserted in the inlet and outlet pipes respectively, to record. the temperature of the heating or cooling liquid. A pipe l3 with valve I4 is connected to the inlet pipe I of the inner vessel and a valve I5 is attached toan extension of inlet pipe I." The outlet pipe 5 has a valve ii to control the flow of solution from the inner vessel. The. outlet pipe 6 also has 'avalv'e I! to control the flow of gas from the inner vessel and a pressure gage l8 for recording the pressure within the vessel 2. A thermocouple or thermometer I9 is inserted in the inner vessel 2 to show the temperature of the liquid.

Figure 2 shows a difierent apparatus for carrying out the same process. An" inner tube 2| is surrounded by a jacket22. This jacket has an inlet pipe 23 and an outlet pipe 24 in which are inserted thermocouples or thermometers 25 and 26 for recording the temperature of the heating fluid. A valve 21' inthef'inlet line controls the flow of this fluid. Y

The inner tube has a lower extension 28 to which an inlet pipe 29 carryin a'reg'ulating valve 30 and a pressure gauge'3l, is attached The lower extension 2 8also"carries a sightglass 32 and a valve 33 for regulating the flow of liquid from theinner tube. An inlet pipe 34 and valve 35 are attached to the upper end of the inner tube as are the outlet pipe 35 and valve 31.

In operating the apparatus shown in Figure 1, water or other heating medium at any desired temperature is passed continuously through the opened enough to Jacket. In order to assist in maintaining the temperature the jacket may beinsulated it desired.

The inner vessel is nlled'with water or other liquid to the level L so that it will just overflow through pipe 5. The trimethylamine and ammonia to be separated are then admitted through valve ll and by keeping valve I! closed, any desired pressure up to the saturationpressure or the solution may be attained. Valve I1 is then keep the pressure reasonably constant. By regulating valves lland I a constant flow of liquid can be maintained through the apparatus.

As the mixture of gases passes through, the more soluble one is concentrated in the liquid and the less soluble one passes through and is removed through valve l1 Alter the apparatus is in operation the flow of liquid and gas mixture are set at constant rates which results in a constant degree of separation of the components of the gas.

The apparatus shown in Figure 2 operates somewhat diflerently. The inner tube It is packed with any ordinary tower packing such as rings, chains, broken tile, etc. Bubble .plates may also be used if desired. Water or other heating or cooling fluid is passed through the jacket so as to maintain the desired temperature within the inner tube II. The gas mixture is admitted at a constant rate through valve Ill and when the desired pressure is attained it is regulated by proper adiustment of the exit valve 31. Water or other absorbing liquid is admitted through valve 35 and pipe 34 and trickles down over the packing through the sight glass 32 and is drawn of! through valve 33.

As the gases and liquid pass in opposite directions the more soluble one is removed by the liquid and the less soluble one passes out through valve 31. Alter the apparatus is in operation the rates of how of gas and liquid are kept constant so that a constant degree of separation of the components of the gas is attained.

The pressure and temperature may be varied over a considerable range without aflecting the emciency of the separation. It is even. possible to adjust them so that two liquid phases are present in the inner tube.

The following examples will serve to illustrate the operation of both types of apparatus but the invention is not limited to the exact conditions of temperature, pressure, rates of flow or composition or the gas mixture given in the examples, as

the invention may be otherwise practiced within the scope of the appended claims.

Example 1.--'I'he same gas mixture as in previous examples was charged to the apparatus shown in Figure 2. The temperature of the water entering the jacket was 93 F. and at the outlet was 118 F. The pressure within the tube was 30 pounds per square inch. Triisobutylene was used as the absorbing liquid and was fed at a rate of 0.47 pound per hour. The gas mixture was fed at 0.23 pound per hour of which 0.074 pound or 32% was absorbed, the remainder passin "through the system. The overhead gas contained 7% trimethylamine and 93% of ammonia or 10%, and 38% respectively of the total amounts ted to the system.

Example 2.-Kerosene was substituted for the triisobutylene and was led at the rate of 0.49 pound per hour. The same gas mixture as previously was fed at the rate of 0.17 pound per hour of which 0.034 or 20% was absorbed. The overhead gas contained 3% oi! trimethylamine and 97% of ammonia and the gases contained in the liquid contained no ammonia. In this case practically a complete separation oi. the two gases was obtained on a single pass through the apparatus.

This application is a continuation-in-part of copending application Serial No. 748,476- filed October 16, 1934 which has matured into U. S. Patent #2,091,630.

-We claim:

1. The process of separating a mixture of trimethylamine and ammonia which comprises selectively absorbing the trimethylamine in an allphatic hydrocarbon solvent by passing the mixture in contact with a stream of said solvent flowing countercurrent thereto.

2. The process of separating a mixture of trimethylamine and ammonia which comprises selectively absorbing the trimethylarnine in kerosene by passing the mixture in contact with a stream of kerosene flowing countercurrent there- 3. The process of separating a mixture of trimethylamine and ammonia which comprises selectively absorbing the trimethylamine in an allphatic hydrocarbon solvent.

4. The processor separating a mixture of trimethylamine and ammonia which comprises selectively absorbing the trimethylamine in kerosene.

MERRELL R. FENSKE. CHESTER E. ANDREWS. 

